scholarly journals Critical role of peroxisome proliferator-activated receptor α in promoting platelet hyperreactivity and thrombosis under hyperlipidemia

Haematologica ◽  
2021 ◽  
Author(s):  
Li Li ◽  
Jiawei Zhou ◽  
Shuai Wang ◽  
Lei Jiang ◽  
Xiaoyan Chen ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Thrombus Formation ◽  
Critical Role ◽  
Dense Granule ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Important Regulator ◽  
Dense Granule Secretion ◽  
Granule Secretion ◽  
Underlying Mechanisms

Platelet hyperreactivity and increased atherothrombotic risk are specifically associated with dyslipidemia. Peroxisome proliferator-activated receptor alpha (PPARα) is an important regulator of lipid metabolism. It was suggested to affect both thrombosis and hemostasis, yet the underlying mechanisms are not well understood. In this study, the role and mechanism of PPARα in platelet activation and thrombosis related to dyslipidemia were examined. Employing mice with deletion of PPARα (Pparα -/-), we demonstrated that PPARα is required for platelet activation and thrombus formation. The effect of PPARα is critically dependent on platelet dense granule secretion, and is contributed by p38MAPK/Akt, fatty acid β- oxidation, and NAD(P)H oxidase (NOX) pathways. Importantly, PPARα and the associated pathways mediated a prothrombotic state induced by high-fat diet (HFD) and platelet hyperactivity provoked by oxidized low density lipoproteins (oxLDL). Platelet reactivities were positively correlated with the expression levels of PPARα, as revealed by data from wild-type (WT), chimeric (Pparα +/-), and Pparα -/- mice. This positive correlation was recapitulated in platelets from hyperlipidemic patients. In a lipid-treated megakaryocytic cell line, lipid-induced reactive oxygen species (ROS)-NF-κB pathway was revealed to upregulate platelet PPARα in hyperlipidemia. These data suggested platelet PPARα critically mediates platelet activation and contributes to prothrombotic status under hyperlipidemia.

scholarly journals Platelet Dense-Granule Secretion Plays a Critical Role in Thrombosis and Subsequent Vascular Remodeling in Atherosclerotic Mice

Circulation ◽  
2009 ◽  
Vol 120 (9) ◽  
pp. 785-791 ◽  
Author(s):  
Sarah M. King ◽  
Rachel A. McNamee ◽  
Aiilyan K. Houng ◽  
Rakesh Patel ◽  
Michael Brands ◽  
...  
Keyword(s):  
Vascular Remodeling ◽  
Critical Role ◽  
Dense Granule ◽  
Dense Granule Secretion ◽  
Granule Secretion

scholarly journals Protein kinase C mediates platelet secretion and thrombus formation through protein kinase D2

Blood ◽  
2011 ◽  
Vol 118 (2) ◽  
pp. 416-424 ◽  
Author(s):  
Olga Konopatskaya ◽  
Sharon A. Matthews ◽  
Matthew T. Harper ◽  
Karen Gilio ◽  
Judith M. E. M. Cosemans ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Molecular Mechanisms ◽  
Thrombus Formation ◽  
Dense Granule ◽  
Molecular Pathway ◽  
Kinase C ◽  
Pkc Isoforms ◽  
Dense Granule Secretion ◽  
Granule Secretion

Abstract Platelets are highly specialized blood cells critically involved in hemostasis and thrombosis. Members of the protein kinase C (PKC) family have established roles in regulating platelet function and thrombosis, but the molecular mechanisms are not clearly understood. In particular, the conventional PKC isoform, PKCα, is a major regulator of platelet granule secretion, but the molecular pathway from PKCα to secretion is not defined. Protein kinase D (PKD) is a family of 3 kinases activated by PKC, which may represent a step in the PKC signaling pathway to secretion. In the present study, we show that PKD2 is the sole PKD member regulated downstream of PKC in platelets, and that the conventional, but not novel, PKC isoforms provide the upstream signal. Platelets from a gene knock-in mouse in which 2 key phosphorylation sites in PKD2 have been mutated (Ser707Ala/Ser711Ala) show a significant reduction in agonist-induced dense granule secretion, but not in α-granule secretion. This deficiency in dense granule release was responsible for a reduced platelet aggregation and a marked reduction in thrombus formation. Our results show that in the molecular pathway to secretion, PKD2 is a key component of the PKC-mediated pathway to platelet activation and thrombus formation through its selective regulation of dense granule secretion.

scholarly journals A dual role for integrin-linked kinase in platelets: regulating integrin function and α-granule secretion

Blood ◽  
2008 ◽  
Vol 112 (12) ◽  
pp. 4523-4531 ◽  
Author(s):  
Katherine L. Tucker ◽  
Tanya Sage ◽  
Joanne M. Stevens ◽  
Peter A. Jordan ◽  
Sarah Jones ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Dense Granule ◽  
Conditional Knockout ◽  
Knockout Mouse Model ◽  
Conditional Knockout Mouse ◽  
Fibrinogen Binding ◽  
Integrin Linked Kinase ◽  
Dense Granule Secretion ◽  
Granule Secretion

Abstract Integrin-linked kinase (ILK) has been implicated in the regulation of a range of fundamental biological processes such as cell survival, growth, differentiation, and adhesion. In platelets ILK associates with β1- and β3-containing integrins, which are of paramount importance for the function of platelets. Upon stimulation of platelets this association with the integrins is increased and ILK kinase activity is up-regulated, suggesting that ILK may be important for the coordination of platelet responses. In this study a conditional knockout mouse model was developed to examine the role of ILK in platelets. The ILK-deficient mice showed an increased bleeding time and volume, and despite normal ultrastructure the function of ILK-deficient platelets was decreased significantly. This included reduced aggregation, fibrinogen binding, and thrombus formation under arterial flow conditions. Furthermore, although early collagen stimulated signaling such as PLCγ2 phosphorylation and calcium mobilization were unaffected in ILK-deficient platelets, a selective defect in α-granule, but not dense-granule, secretion was observed. These results indicate that as well as involvement in the control of integrin affinity, ILK is required for α-granule secretion and therefore may play a central role in the regulation of platelet function.

scholarly journals Misshapen/NIK-related kinase (MINK1) is involved in platelet function, hemostasis, and thrombus formation

Blood ◽  
2016 ◽  
Vol 127 (7) ◽  
pp. 927-937 ◽  
Author(s):  
Ming Yue ◽  
Dongjiao Luo ◽  
Shanshan Yu ◽  
Pu Liu ◽  
Qi Zhou ◽  
...  
Keyword(s):  
Platelet Function ◽  
Thrombus Formation ◽  
Dense Granule ◽  
Key Points ◽  
Dense Granule Secretion ◽  
Granule Secretion

Key Points MINK1 promotes hemostasis and thrombosis in vivo. MINK1 specifically regulates platelet dense-granule secretion.

ELMO1 Is a Novel Negative Regulator of Glycoprotein VI Signaling in Platelets

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 2533-2533
Author(s):  
Akruti Patel ◽  
Soochong Kim ◽  
John Kostyak ◽  
Rachit Badolia ◽  
Carol Dangelmaier ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Thrombus Formation ◽  
Dense Granule ◽  
Negative Regulator ◽  
Related Protein ◽  
Rac1 Activity ◽  
Dense Granule Secretion ◽  
Granule Secretion ◽  
Deficient Mice

Abstract PI3-kinase (phosphoinositide 3-kinase) is an important signaling molecule that is activated downstream of various receptors upon platelet activation. PI3-kinase activation leads to the generation of PIP3 (Phosphatidylinositol (3,4,5)-trisphosphate) subsequently leading to the recruitment of PH (pleckstrin homology) domain containing proteins to the plasma membrane. Our laboratory screened for proteins that interacted with PIP3 (Phosphatidylinositol (3,4,5)-trisphosphate) using PIP3 beads. One of the proteins that interacted with PIP3 was ELMO1 (Engulfment and cell motility-1). ELMO1 is a scaffold protein with no catalytic activity and is well known to regulate actin cytoskeletal rearrangement via Rac1 in other cells. However, it is not known whether ELMO1 is expressed in platelets and if so, does it regulate platelet functional responses. Here, we show that ELMO1 is present in both human and murine platelets. We used ELMO1-deficient (ELMO1-/-) mice to study its role in platelets. ELMO1-/- murine platelets showed enhanced platelet aggregation and dense granule secretion in response to the GPVI agonist, CRP (Figure 1 A & B), compared to the wildtype controls although there was no difference in GPVI expression levels between the two. There was no difference observed in response to AYPGKF- or 2-MeSADP. These data suggest that ELMO1 plays a specific role downstream of GPVI pathway but GPCRs. Moreover, ELMO1-/- platelets exhibited enhanced clot retraction and spreading indicating its role in Glycoprotein IIb/IIa (GPIIb/IIIa) mediated outside-in signaling. Furthermore, whole blood from ELMO1-/- mice perfused over collagen under arterial shear conditions exhibited enhanced thrombus formation. In an in vivo pulmonary thromboembolism model, ELMO1-/- mice showed reduced survival compared to the wildtype control. ELMO1-/- mice also showed shorter time to occlusion and increased thrombus stability using the ferric-chloride injury model indicating the role of ELMO1 in thrombus formation in vivo. At the molecular level, Rac1 activity was enhanced in ELMO1-/- murine platelets compared to the wildtype control in response to CRP (Figure 1C). Together, these data suggest that ELMO1 regulates Rac1 activity upon GPVI-mediated thrombus formation and it may play a negative regulator role in both inside-out and outside-in signaling, which might involve Rac1. Figure 1 Representative figure of (A) platelet aggregation and (B) dense granule secretion. (C) Washed platelets were stimulated with CRP 1.25 μg/mL for the indicated times. GST-PAK-RBD was used to pull-down active Rac1 from platelet lysates and was detected using specific antibody to Rac1 by Western blot. WT = Wildtype mice. ELMO1-/- = ELMO1-deficient mice. CRP = collagen related protein. Figure 1. Representative figure of (A) platelet aggregation and (B) dense granule secretion. (C) Washed platelets were stimulated with CRP 1.25 μg/mL for the indicated times. GST-PAK-RBD was used to pull-down active Rac1 from platelet lysates and was detected using specific antibody to Rac1 by Western blot. WT = Wildtype mice. ELMO1-/- = ELMO1-deficient mice. CRP = collagen related protein. Disclosures No relevant conflicts of interest to declare.

scholarly journals PCTP contributes to human platelet activation by enhancing dense granule secretion

2021 ◽  
Vol 202 ◽  
pp. 67-73
Author(s):  
Shaji Abraham ◽  
Lin Ma ◽  
Xianguo Kong ◽  
Shayan Askari ◽  
Leonard C. Edelstein ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Human Platelet ◽  
Dense Granule ◽  
Dense Granule Secretion ◽  
Granule Secretion

Granules and thrombus formation

Blood ◽  
2009 ◽  
Vol 114 (5) ◽  
pp. 932-933 ◽  
Author(s):  
Walter H. A. Kahr
Keyword(s):  
Thrombus Formation ◽  
Dense Granule ◽  
Snare Protein ◽  
Laser Injury ◽  
Platelet Accumulation ◽  
Dense Granule Secretion ◽  
Granule Secretion

In this issue of Blood, Graham and colleagues demonstrate the importance of platelet dense granule secretion for in vivo platelet accumulation following laser injury, which is mediated by the SNARE protein Endobrevin/VAMP-8.

Platelet 12-Lipoxygenase Is Required for Dense Granule Secretion and Platelet Aggregation: Role of 12-hLO In Platelet Hemostasis and Thrombosis

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3203-3203
Author(s):  
Patrick Apopa ◽  
Megha Patel ◽  
Olivier Boutaud ◽  
Michael Holinstat
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Platelet Reactivity ◽  
Dense Granule ◽  
Clot Formation ◽  
Dense Granule Secretion ◽  
Granule Secretion ◽  
12 Lipoxygenase

Abstract Abstract 3203 Platelet activation plays a central role in regulating hemostasis. Uncontrolled activation of circulating platelets can result in the formation of occlusive thrombi and stroke. Following activation, metabolism of arachidonic acid by 12-lipoxygenase (12-hLO) may play a significant role in regulating the degree and stability of platelet reactivity. Using specific inhibitors for 12-hLO which do not interact with other lipoxygenases or enzymes in the COX-1 pathway, we were able for the first time to asses the involvement of 12-hLO in platelet reactivity. In order to assess the role of 12-hLO in platelet activation and thrombosis, dense granule secretion, platelet aggregation, alpha granule secretion, and platelet adhesion and clot formation under flow were measured. Inhibiting 12-hLO results in a complete inhibition of dense granule secretion with only a partial attenuation of alpha granule secretion indicating a novel regulatory scheme for modulating positive autocrine reinforcement of platelet reactivity and clot formation. Addition of the 12-hLO metabolite, 12-HETE (as low as 250 nM), resulted in a significant (25%) increase in PAR1-mediated dense granule secretion compare to agonist alone indicating that 12-HETE may be the crucial metabolite formed by 12-hLO metabolism of arachidonic acid. Importantly, platelet aggregation and adhesion are also significantly attenuated in the absence of 12-hLO. In fact, collagen-mediated platelet aggregation was shifted over 25 fold to the right in the absence of 12-hLO. These studies support the role of 12-hLO in hemostasis and may be a good target for anti-platelet therapy. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Analysis of microvascular thrombus mechanobiology with a novel particle-based model

2021 ◽  
Author(s):  
Anastasia A Masalceva ◽  
Valeriia N Kaneva ◽  
Mikhail A Panteleev ◽  
Fazoil Ataullahanov ◽  
Vitaly Volpert ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Dense Granule ◽  
Aggregate Formation ◽  
Mechanical Stabilization ◽  
Dense Granules ◽  
Virtual Particles ◽  
Platelet Accumulation ◽  
Dense Granule Secretion ◽  
Granule Secretion

Platelet accumulation at the site of vascular injury is regulated by soluble platelet agonists, which induce various types of platelet responses, including integrin activation and granule secretion. The interplay between local biochemical cues, mechanical interactions between platelets and macroscopic thrombus dynamics is poorly understood. Here we describe a novel computational model of microvascular thrombus formation for detailed analysis of thrombus mechanics. Adopting a previously developed two-dimensional particle-based model focused on the thrombus shell formation, we revise it to introduce platelet agonists. Blood flow is simulated via computational fluid dynamics approach. In order to model soluble platelet activators, we apply Langevin dynamics to a large number of non-dimensional virtual particles. Taking advantage of the available data on platelet dense granule secretion kinetics, we model platelet degranulation as a stochastic agonist-dependent process. The new model qualitatively reproduces enhanced thrombus formation due to granule secretion in line with in vivo findings and provides a mechanism for thrombin confinement at the early stages of aggregate formation. Our calculations also predict that release of dense granules results in additional mechanical stabilization of the inner layers of the thrombus. Distribution of the inter-platelet forces throughout the aggregate reveals multiple weak spots in the outer regions of thrombus, which are expected to result in mechanical disruptions at the later stages of thrombus formation.

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